This invention relates to an input setting method for digital operational devices which method is adapted for use in process controls and system controls and more specifically for use in a controlled protective relaying apparatus for protecting an electric power transmission system.
Recently electronic computers have been widely used for process controls and system controls, and various modifications of minicomputers and microcomputers which are adapted for various applications have been proposed. Although these modified minicomputers and microcomputers may be called electronic computers, they are hereinafter termed "digital operational devices" because of their minor deviations from ordinary electronic computers.
In order to improve its reliability, each digital operational device is usually provided with a device for supervising the internal operation thereof. However, it is difficult to supervise the input setting operation of the digital operational device because the input setting values are varied unpredictably. thus, it is impossible to judge whether the input setting values (or data) are correct or not, and to detect an erroneous input when it occurs.
In the case where a digital control device is used with a relaying apparatus, as disclosed in U.S. Pat. No. 3,984,737, to protect an electric power transmission system, the adverse effects caused by the erroneous setting are serious, and in the worst case, the stability of the entire power transmission system will be lost.